1. Technical Field
The present invention relates to a discharge lamp lighting device, a discharge lamp lighting method, and a projector.
2. Related Art
A projector including a discharge lamp such as a high pressure mercury lamp as a light source is known. The projector of this type includes a resonance circuit in order to obtain a high voltage for starting electric discharge of the discharge lamp (see, for example, JP-A-2007-27145 (Patent Literature 1)). In such a projector, when the discharge lamp is lit, a high voltage can be obtained by adjusting a frequency of alternating-current power supplied to the discharge lamp to a resonance frequency of the resonance circuit. After the discharge lamp starts the electric discharge and is lit, the frequency of the alternating-current power supplied to the discharge lamp is reduced. Electric power during steady lighting is given to the discharge lamp.
Individual differences and aged deteriorations are present in an inductance component and a capacitance component of the resonance circuit. Therefore, if the frequency of the alternating-current power supplied to the resonance circuit is fixed when the discharge lamp is lit, it is likely that resonance does not occur and, as a result, the discharge lamp is not lit. In order to prevent such a problem, in the technique disclosed, in Patent Literature 1, every time the discharge lamp is lit, an actual resonance frequency is found by monotonously increasing the frequency of the alternating-current power supplied to the discharge lamp to the resonance frequency.
However, with the method of monotonously changing the frequency of the alternating-current power supplied to the discharge lamp, the resonance circuit is placed in a quasi-resonance state until the discharge lamp is lit. In such a state, a voltage and an electric current in the resonance circuit increase. A switching loss of a bridge circuit or the like that generates the alternating-current power supplied to the resonance circuit also increases. Therefore, power consumption in lighting the discharge lamp increases.